1. Field of the Invention
The present invention relates to an ultrasonic driving apparatus.
This application is based on Japanese Patent Application No. 2005-021561, the content of which is incorporated herein by reference.
2. Description of Related Art
Recently, ultrasonic motors (ultrasonic driving apparatuses) using the vibration of an oscillator such as a piezoelectric device have been receiving attention as new types of motor for replacing electromagnetic motors. These ultrasonic motors have numerous advantages, including their low speed and high thrust without a gear, high holding power, long stroke, high resolution, quiet operation, absence of electromagnetic noise produced, imperviousness to electromagnetic noise, and so forth.
Among the advantages mentioned above, in order to exhibit, in particular, superior positioning performance such as high resolution, it is necessary to position the oscillator of the ultrasonic motor with high precision.
However, when the oscillator is fixed to an attachment member or the like having high rigidity, there is the drawback that the generation of vibrations by the oscillator is inhibited, which deteriorates the performance of the ultrasonic motor. Moreover, when fixing the oscillator to an elastic member or the like in order not to inhibit the generation of vibrations by the oscillator, there is the problem of deteriorated positioning precision due to deformation of the elastic member and so forth.
Therefore, a holding structure and a holding method have been proposed for setting the position of the oscillator in the ultrasonic motor with high precision without inhibiting the generation of vibrations by the oscillator.
Japanese Unexamined Patent Application Publication No. 2004-96984 discloses a technology using an urging member, such as a pin, for pushing the oscillator against a driven member to position the oscillator.
However, when positioning the oscillator using the urging member, there is a problem in that it is difficult to improve the positioning precision. Specifically, although the urging member is endowed with elasticity for urging the oscillator, since this elasticity permits motion of the oscillator, there is a problem in that the positioning precision of the oscillator is reduced.